1. Technical Field
The present invention relates to a dental casting billet material, a metal powder for powder metallurgy, a dental metal component, and a dental prosthesis.
2. Related Art
When a tooth in the mouth is lost, by attaching a denture, mastication and vocalization can be maintained, or facial appearance can be fixed. The denture includes a denture base and an artificial tooth planted in the denture base. Among these, as the denture base, a metal base formed from a metal material and a resin base formed from a resin material are known. The metal base can be made sufficiently thin as compared with the resin base, and therefore has advantages that when the metal base is attached in the mouth, the sense of discomfort felt by a patient is reduced, or it is less likely to become an obstacle when a patient talks.
In addition, the metal base has a sufficiently high strength derived from a metal material. Due to this, the metal base also has advantages that it is difficult to bend and also it is less likely to adversely affect remaining teeth and gums when it is attached.
As a constituent material of such a metal base, for example, a cobalt-chromium alloy, a noble metal alloy, a titanium alloy, and the like are known. Among these, a cobalt-chromium alloy has relatively high chemical stability, and also is easily available, and therefore has been widely used.
JP-A-2006-328475 (PTL 1) discloses a Co—Cr alloy pellet having a composition of C (0.10% or more and 0.60% or less), Si (0.50% or more and 1.50% or less), Mn (0.05% or more and 0.50% or less), Cr (26.00% or more and 35.00% or less), Mo (4.00% or more and 7.00% or less), and N (0.30% or more and 1.60 or less).
When a metal base is produced by using a cobalt-chromium alloy, a lost-wax casting method is generally used. This method is performed as follows. First, a model which reproduces the shape in the mouth is produced. Subsequently, the shape of this model is copied into a wax. The thus obtained wax model is covered with a fire resistant material, followed by firing. By doing this, the wax model disappears, and a mold having a cavity corresponding to the wax model is obtained. Subsequently, a metal melt (molten metal) of a cobalt-chromium alloy is poured into the cavity of this mold, whereby a metal base having a desired shape is produced by casting.
In such a casting method, when a gap of the cavity is small, a metal melt sometimes cannot enter the cavity. When such a trouble occurs, a metal base having a desired shape cannot be produced. Due to this, in order to fill a metal melt in the cavity regardless of the shape of the cavity, the metal melt fluidity (flowability) needs to be high. However, the metal melt obtained by melting the Co—Cr alloy pellet disclosed in PTL 1 has low melt fluidity, and therefore, depending on the shape of the cavity, it is sometimes difficult to fill the metal melt in the cavity to every corner.